Other people try to explain the low wages by looking at the motivation of the workers: Quite a few people find the tasks on Mechanical Turk to be interesting. Ergo, they are willing to work for less.

Perfectly normal right? The task is interesting, people are willing to do it for less money. Sounds reasonable. Right? RIGHT? Well, be careful: correlation does not imply causation!

Enter the region of social psychology (thanks Konstantinos!): The theory of cognitive dissonance indicates that the causation may go in the entirely opposite direction: The wages are low, so people justify their participation by saying the work is interesting!

That people that get low payment to do boring tasks, will convince themselves that they do this because the task is interesting. Otherwise, the conflict in their mind will be just too big: why do they work on such a boring task when the payment is horrible?

In contrast, if someone gets paid well to do the same boring task, they will consider the task boring. These well-paid participant can easily justify that they do the work for the money, (so it makes sense to do a boring job).

Students were asked to spend an hour on boring and tedious tasks (e.g., turning pegs a quarter turn, over and over again). The tasks were designed to generate a strong, negative attitude.

Once the subjects had done this, the experimenters asked some of them to do a simple favor. They were asked to talk to another subject (actually an actor) and persuade them that the tasks were interesting and engaging.

Some participants were paid $20 (inflation adjusted to 2010, this equates to $150) for this favor, another group was paid $1 (or $7.50 in "2010 dollars"), and a control group was not asked to perform the favor.

When asked to rate the boring tasks at the conclusion of the study (not in the presence of the other "subject"), those in the $1 group rated them more positively than those in the $20 and control groups.

The researchers theorized that people experienced dissonance between the conflicting cognitions, "I told someone that the task was interesting", and "I actually found it boring." When paid only $1, students were forced to internalize the attitude they were induced to express, because they had no other justification.Those in the $20 condition, however, had an obvious external justification for their behavior (i.e., high payment), and thus experienced less dissonance.

So, when you read surveys (mine included) that indicate that Mechanical Turk workers participate on the platform because they "find the tasks interesting", (and so it makes sense to pay low wages), please have this alternative explanation in mind:

Turkers convince themselves that the work is interesting, otherwise they would be completely crazy sitting there doing mind-boggling boring work, just to earn wage of a couple of bucks per hour.